1. Field
This disclosure is concerned generally with an improved transferrin preparation and specifically with a method and composition comprising a virally inactivated, non-toxic transferrin preparation for use in cell culture systems.
2. Prior Art
Transferrins are iron-binding glycoproteins having molecular weights of 76,000-81,000. Serum transferrin is also referred to as B.sub.1 -metal combining protein or siderophilin. Transferrin is well know as an important, if not essential, supplement to serum-free media. Although the function of transferrin has yet to be resolved, it is believed to act as a growth factor, to provide cells with iron and to detoxify media by binding contaminating metal ions. These theories have been proposed by J. Kovar and F. Franek in "Hybridoma Cultivation in Defined Serum-Free Media:Growth-Supporting Substances", I. Transferrin, Folia Biol (Praha):31 (2):167-75, 1985.
Bovine and human transferrin products are available commercially. Suppliers include Miles Diagnostics, Kankakee, Ill.; Leon Laboratories, Ft. Lauderdale, Fla.; and Boehringer Mannheim Biochemicals, Indiana.
Presently, bovine transferrin is the prior art transferrin of choice since bovine are not susceptible to human viral contamination such as hepatitis and HIV. A drawback to using bovine transferrin in cell culture systems in the problem of species antigenicity. This is an even bigger drawback when the end product will be introduced into humans.
The prior art human transferrin products available are not viral-inactivated nor are they non-toxic to the cell culture systems.
U.S. Pat. No. 2,955,074 relates to a method of virally inactivating iron-binding glycoproteins and then removing the bound iron so that radioactive isotopes can be bound to the transferrin. The bound iron is removed by a chelating agent. This method was also used by H. G. Wada, P. E. Hass, and H. H. Sussman, in "Transferrin Receptor in Human Placental Brush Border Membranes", J. Biol. Chem., Vol. 254, No. 24, pp. 12,629-12,635, 1979. The method of U.S. Pat. No. 2,955,074 and of Wada, teach processing the transferrin after pasteurization which can result in contamination of the transferrin preparation with viral and microbial contaminants.